<p>Genjutsu is exceedingly hard to pull off because you have to fool the senses. SOmething as easy as forgetting a shadow can tip off a Shinobi that they're in a Genjutsu. </p><p>The Sharingan takes in all details at once, so Sharingans can usually detect Genjutsu is happening immediately. Once that's done, a simple disruption of their own chakra frees them from the Genjutsu. </p><p>Idk what you mean when you're saying the victim's chakra can't be irregular; do you mean when they're in a Genjutsu? </p><p>You don't have to stop the flow of chakra from the castor. You have to disrupt the victim's chakra by injecting your own or in the victim's case, disrupting their own. </p>

<p>Well, to be honest, there are other types of genjutsu that can easily be figured out as one, but still be unable to be countered with. Like Jiraya's and the Sound Ninja's genjutsu, which captyres the person, and even though they know they're in it, they are stuck. And just like that, there is the Sharingan Genjutsu which kind of treats the opponents into mental pain that is felt physically or something, like the Tsukuyomi and the genjutsu Sasuke did with C and Sakura. And then, there is the controlling one. Which kind of works with target being unconscious of whatever he or she is doing, like with Kurama, Manda, and many other examples. </p>